# How to train the classifier for V3-V4 region with 99% identity using full length seuqnces from new relase of GreenGenes-2022??

**URL:** https://forum.qiime2.org/t/how-to-train-the-classifier-for-v3-v4-region-with-99-identity-using-full-length-seuqnces-from-new-relase-of-greengenes-2022/27991
**Category:** Library Support
**Tags:** taxonomy, feature-classifier, greengenes
**Created:** [October 18, 2023, 6:37am UTC](https://forum.qiime2.org/t/how-to-train-the-classifier-for-v3-v4-region-with-99-identity-using-full-length-seuqnces-from-new-relase-of-greengenes-2022/27991 "2023-10-18T06:37:45Z")
**Posts on this page:** 1
**Showing post:** 7

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### Author: ![buzic](https://forum.qiime2.org/user_avatar/forum.qiime2.org/buzic/32/16494_2.png) [@buzic](https://forum.qiime2.org/u/buzic)
#### Post date: [October 23, 2023, 2:31pm UTC](https://forum.qiime2.org/t/how-to-train-the-classifier-for-v3-v4-region-with-99-identity-using-full-length-seuqnces-from-new-relase-of-greengenes-2022/27991/7 "2023-10-23T14:31:26Z")

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Hi,

the readme file looks like you'd need the following files:

2022.10.backbone.full-length.fna.qza  
2022.10.backbone.tax.qza

The following method should help point you in the right direction. First take the sequence files and trim them based on your primers (obviously I've just added a random sequence here!). You can also add truncation and min/max lengths of sequences based on your experimental design, for example:

```auto
qiime feature-classifier extract-reads \
  --i-sequences 2022.10.backbone.full-length.fna.qza \
  --p-f-primer GTGGTGGTGGTGGTGGTG \
  --p-r-primer GGACTGGACTGGACTGGA \
  --p-min-length 100 \
  --p-max-length 600 \
  --o-reads gg_12_10_ref_primer_region_seqs.qza

```

then use your newly trimmed sequence file along with the backbone taxonomy to train your classifier:

```auto
qiime feature-classifier fit-classifier-naive-bayes \
  --i-reference-reads gg_12_10_ref_primer_region_seqs.qza \
  --i-reference-taxonomy 2022.10.backbone.tax.qza \
  --o-classifier gg_12_10_primer_region-classifier.qza

```

I hope that helps, there are lots of walkthroughs and helpful documents in the qiime2 forum and docs, for example [here](https://docs.qiime2.org/2023.9/tutorials/feature-classifier/)

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